1. Field of the Invention
The present invention relates to a lighting control apparatus and a method of lighting control for a vehicle lighting device and, in particular, relates to a lighting control apparatus and method of lighting control for a vehicle lighting device which is configured to control the lighting of a semiconductor light source constituted by a semiconductor light emitting element.
2. Background Art
There has been known a vehicle lighting device which employs a semiconductor light emitting element such as a light emitting diode (LED). In such a vehicle lighting device, a lighting control circuit for controlling the lighting of the LED is mounted.
In such a case, the lighting control circuits constituted of a configuration arranged in a manner that a plurality of LEDs are coupled in series to constitute a light source unit, a plurality of the light source units are coupled in parallel, the lighting control circuit is coupled to the both ends of the plurality of the light source units coupled in parallel, the lighting control circuit supplies the same current to all of the LEDs of the plurality of the light source units, and a resistor is inserted in series in each of the plurality of the light source units. In the case where a voltage across the both terminals of the resistor drops, for example, when the current stops flowing trough the resistor due to the breakage of one of the LEDs of the light source units and so the voltage across the both terminals of the resistor becomes 0 volts, one of the LEDs of the light source units is determined to be broken and the output voltage of a switching regulator constituting the lighting control circuit is reduced (see patent document 1). According to such a lighting control circuit, when one of the LEDs of the light source units is broken, the output voltage of the switching regulator is reduced, so that the output voltage of the switching regulator is prevented from being an overvoltage or excess voltage.
[Patent Document 1] JP-A-2004-134147 (pages 3 to 6, FIG. 1)